The present invention relates to a clutch unit for transmitting/cutting off a torque between an input side member and an output side member through an engaging element.
A mechanical clutch using an engaging element such as a roller or a ball controls transmission/blocking of a torque by engaging/disengaging the engaging element into a wedge-shaped clearance formed between an input side member and an output side member. More specifically, the engagement of the engaging element into the wedge-shaped clearance locks the input side member and the output side member through the engaging element, so that a torque is transmitted between these members through the engaging element. The disengagement of the engaging element from the wedge-shaped clearance allows the input side member and the output side member to run idle relative to each other, so that the torque is cut off between these members. The engagement/disengagement of the engaging element to/from the wedge-shaped clearance is automatically switched by switching the rotation direction in some cases and by pivoting a retainer retaining the engaging element in other cases.
For example, in a unit which positions or adjusts the position of members by transmitting an input torque produced by the pivotal movement of an operation member to the output side mechanism, when the pivotal movement is completed and the operation member is released, the position of the output side mechanism must be held while the operation member must automatically regain the original position.
It is an object of the present invention to provide a clutch unit capable of achieving the above-described function.
In order to achieve the above-described object, the present invention provides a structure including an input side member having a cam surface, an output side member having a circumferential surface, an engaging element interposed between the cam surface of the input side member and the circumferential surface of the output side member, a retainer for retaining the engaging element, and an elastic member for coupling the retainer to a stationary side member in the pivotal direction.
Herein, the xe2x80x9cinput side memberxe2x80x9d refers to a member provided with an input torque through an operation member or the like. The input side member has a cam surface forming a wedge-shaped clearance between the circumferential surface of the output side member and itself. The cam surface may directly be provided at an axial member, or a ring shaped member having a cam surface fixed at an axial member may be employed.
The xe2x80x9coutput side memberxe2x80x9d pivots together with the input side member through the engaging/disengaging function of the engaging element, while runs idle relative to the input side member. The output side member has a circumferential surface. The circumferential surface may be provided directly at an axial member or a ring shaped member having a circumferential surface fixed at an axial member may be employed.
The xe2x80x9cengaging elementxe2x80x9d is applicable to a roller shaped member or a ball shaped member, or the like.
In the above construction, when an input torque is provided to the input side member, the cam surface moves relative to the engaging element in the pivotal direction as the input side member pivots. The rollers thus engage with the wedge-shaped clearances. Thus, the input torque from the input side member is transmitted to the output side member through the engaging element. Then, the input side member, the engaging element, the retainer and the output side member pivot together. As the retainer pivots, the elastic member coupling the retainer to the stationary side member in the pivotal direction deflects, and the elastic force corresponding to the deflection amount is accumulated at the elastic member. When the input side member is allowed to pivot for a prescribed amount and then released, the elastic force accumulated at the elastic member causes the pivotal force to act upon the retainer. The engaging element is pressed by the retainer to press the cam surface, so that the engaging element, the retainer and the input side member run idle relative to the output side member and regain the original positions.
In the above construction, a wedge-shaped clearance may be formed in both normal and reverse directions between the cam surface of the input side member and the circumferential surface of the output side member. Thus, the above-described function may be achieved to an input torque in the normal and reverse directions.
Also in the above construction, a stopper portion for restricting the pivotal range of the input side member may be provided. Thus, the input side member does not excessively pivot and therefore no excess force acts upon the elastic member.
According to the present invention, a clutch unit capable of transmitting an input torque from the input side member to the output side member, while maintaining the pivotal position of the output side member, and automatically returning the input side member to the initial position can be provided.
The nature, principle, and utility of the invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings in which like parts are designated by like reference numerals or characters.